1. Field of the Invention
The present invention relates to a method for determining whether a photographic image is a different-color structure photographic image and a photographic image processing apparatus.
2. Description of the Related Art
Normally, a film used for photography is referred to as “a daylight film”. If photography is performed with a solar light or a strobe light, a photograph having an appropriate color balance is obtained. However, since photography is performed in various situations, inappropriate images are, quite often, recorded on a film. Examples of photographic scenes include a scene photographed with a tungsten light, a scene photographed with a fluorescent light, a scene photographed underwater, and the like. Thus, scenes are photographed using different light sources. For example, a photographic image photographed with the tungsten light is generally yellowish and that photographed with the fluorescent light or photographed underwater is generally bluish.
As a conventional method for determining whether photographic images are photographed using different types of light sources, a technique for estimating a type of a light that illuminates a subject based on average brightness information during photography and presence or absence of a flash light is disclosed by Japanese Unexamined Patent Publication No. 7-219077.
However, the method disclosed by Japanese Unexamined Patent Publication No. 7-219077 has a disadvantage in that a different-type-light-source photographic image and a different-color structure photographic image cannot be accurately discriminated from each other. The “different-color structure” means herein a specific object if a main subject is not influenced by a photographic light source but the specific object obviously different in colors from the subject largely occupies an image plane. As different-color structure scene, the following two types of scenes are known. One is an ordinary scene, as shown in, for example, a left photograph of FIG. 11B, in which a yellow structure is present. The other is a scene in which, for example, a person is present in front of a tank in an aquarium or the like. With the conventional method, if a different-color structure photographic image of a scene, for example, in which a yellow signboard is present is erroneously determined as a photograph taken by the tungsten light, and if image data is corrected based on such a determination result, a color failure disadvantageously occurs. Due to this, there is no avoiding finally adjusting a color balance by a manual operation by, for example, allowing an operator to observe an image of each frame to determine whether the image is a different-color structure photographic image or a different-type-light-source photographic image. If the operator determines that the image is a different-type-light-source photographic image, the operator adds a density of yellow if the image is yellowish like a photograph taken by a tungsten light, and a density of blue if the image is bluish like a photograph taken underwater.